From cff857461be443339aa39d614635d9a4eae8f8b2 Mon Sep 17 00:00:00 2001
From: Michael Brown
Date: Wed, 15 Feb 2023 22:43:33 +0000
Subject: [rng] Add RDRAND as an entropy source

Signed-off-by: Michael Brown <mcb30@ipxe.org>
---
 src/arch/x86/include/ipxe/cpuid.h  |  3 +++
 src/arch/x86/include/ipxe/rdrand.h | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+)
 create mode 100644 src/arch/x86/include/ipxe/rdrand.h

(limited to 'src/arch/x86/include/ipxe')

diff --git a/src/arch/x86/include/ipxe/cpuid.h b/src/arch/x86/include/ipxe/cpuid.h
index 3983dfb89..90d1bf01d 100644
--- a/src/arch/x86/include/ipxe/cpuid.h
+++ b/src/arch/x86/include/ipxe/cpuid.h
@@ -39,6 +39,9 @@ struct x86_features {
 /** Get standard features */
 #define CPUID_FEATURES 0x00000001UL
 
+/** RDRAND instruction is supported */
+#define CPUID_FEATURES_INTEL_ECX_RDRAND 0x40000000UL
+
 /** Hypervisor is present */
 #define CPUID_FEATURES_INTEL_ECX_HYPERVISOR 0x80000000UL
 
diff --git a/src/arch/x86/include/ipxe/rdrand.h b/src/arch/x86/include/ipxe/rdrand.h
new file mode 100644
index 000000000..c9c170fb0
--- /dev/null
+++ b/src/arch/x86/include/ipxe/rdrand.h
@@ -0,0 +1,37 @@
+#ifndef _IPXE_RDRAND_H
+#define _IPXE_RDRAND_H
+
+/** @file
+ *
+ * Hardware random number generator
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <stdint.h>
+#include <ipxe/drbg.h>
+
+#ifdef ENTROPY_RDRAND
+#define ENTROPY_PREFIX_rdrand
+#else
+#define ENTROPY_PREFIX_rdrand __rdrand_
+#endif
+
+/**
+ * min-entropy per sample
+ *
+ * @ret min_entropy	min-entropy of each sample
+ */
+static inline __always_inline min_entropy_t
+ENTROPY_INLINE ( rdrand, min_entropy_per_sample ) ( void ) {
+
+	/* Data returned by RDRAND is theoretically full entropy, up
+	 * to a security strength of 128 bits.
+	 */
+	if ( DRBG_SECURITY_STRENGTH > 128 )
+		return 0;
+	return MIN_ENTROPY ( 8 * sizeof ( noise_sample_t ) );
+}
+
+#endif /* _IPXE_RDRAND_H */
-- 
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